IN TR O D U C TIO N
1
They lead a life in the shadow s,
but they are m ore im portant than
any luxury accessories:
Fi l t e rs
Filters purify the substances that are
necessary for proper engine opera-
tion. A failure to observe the m ain-
tenance intervals or a lack of lter
quality frequently lead to enorm ous
follow -up costs. Filtration has becom e
very extensive in m odern vehicles
due to the constantly rising require-
m ents on the engines. H igh custom er
dem ands as w ell as stringent environ-
m ental regulations are further factors
that have a great inﬂ uence on the
developm ent of lter technology.
1.1 General remarks
G enerally speaking, lters have the
function of preventing im purities and
foreign m atter from entering the
inside ot the engine together w ith the
air, oil and fuel.

In engine technology, different types
of lters are used for the various sub-
stances to be ltered. They differ w ith
respect to their function, structure,
and m aintenance intervals.
There are num erous ltration
m ethods: D irt particles can be rem o-
ved by using
■ ﬁ ne-m eshed plastic
or m etal sieves,
■ ﬁ ne-porous paper, felt
and eece or
■ through centrifugal forces.
1.2 KS ﬁlter classiﬁcation
The KS range of lters com prises air,
oil and fuel lters for passenger cars,
trucks, and for utility vehicle applica-
tions. According to the type of appli-
cation, the lters are classi ed as fol-
low s:
1.3 Wear in an internal
combustion engine
W henever m oving parts com e into
contact or m esh, they cause friction
w hich m ust be avoided. A s a sui-
table lubricant, m ineral or synthetic
oil is used w hich form s a sliding
ﬁ lm betw een the m achine parts. This
ultra-thin separation lm acts as a
buffer to prevent a direct contact
and to allow an easy sliding of the
parts. O f course, this lubrication is
only possible if the oil does not con-
tain contam inants. Even im purities of
m icroscopic size m ay not be carried
because, as abrasive particles, they
enorm ously accelerate the abrasive
w ear of the engine parts.
C ritical spots w ithin the engine are
the cylinder barrels, pistons, piston
rings, valves, gaskets, crankshafts
and connecting rod bearings.
Im purities can enter the engine
directly in the form of sand or sand
particles w ith the fuel of the intake
air.
In addition, the engine creates its
ow n contam inants in the form of ne
m etal abrasives, residues
of incom plete com bustion
or sm all bres, plastic
or rubber particles. These
im purities also have a
w ear-enhancing effect on
the system and m ay even
cause operation failures.
Sectional view of an internal combustion engine
OS oil spin-on spin-on oil ﬁlter
OC oil cartridge oil ﬁlter cartridge
OH oil hydraulic hydraulic oil ﬁlter
OX oil metalfree oil ﬁlter cartridge, metal-free
E... ENERGETIC
®
ENERGETIC
®
AP air panel panel air ﬁlter
AR air round round air ﬁlter
AD air dryer air dryer
FS fuel spin-on spin-on fuel ﬁlter
FC fuel cartridge fuel ﬁlter cartridge
FP fuel pipe (inline) fuel pipe ﬁlter
FX fuel metalfree fuel ﬁlter cartridge, metal-free
5
W EA R IN A N IN TER N A L C O M B U STIO N EN G IN E
New component
The dirt lm w hich has settled on the lter during a m ile-
age of 15,000 km is clearly visible. M inute dirt particles
settle in the depth structure of the lter paper.
C onsequences: richer fuel-air m ixture, elevated pollutant
em ission, low er engine perform ance.
Strong scoring on the m ain bearing,
caused by an abrasive m ass consi-
sting of oil and dirt particles.
C onsequence: engine failure
1.4 Wear of engine components due to
impurities in the system
Enorm ous w ear on the edges of the
oil scraper ring.
C onsequence: elevated oil con-
sum ption.
Damaged component
6
N ew cylinder sleeve w ith a clearly
visible cross hatch. This surface,
produced by using a honing tool,
im proves the oil adhesion on the
inside w all of the cylinder.
C ylinder sleeve w ith scoring on the
inside w all. The honing pattern is not
perceptible any m ore.
C onsequence: elevated oil con-
sum ption
W EA R IN A N IN TER N A L C O M B U STIO N EN G IN E
M arked w ear in the area of the 1st
ring groove. The elevated clearance
leads to a low er com pression, cau-
sing a loss of pow er.
U sed piston w ith clear signs of w ear.
Strong abrasion of the graphite lm
on the piston body.
The m issing sliding lm m ay lead
to piston m alfunction or even piston
seizing.
New component Damaged component
Detail Detail
7
B A SIC S O F FILTR ATIO N
2
W hen talking of ltration in
m odern vehicles, the m ain focus
lies on depth lters. These special
ﬁ lter elem ents are used if particles
are to be rem oved from liquids (oil
and fuel) or gases (air) at 100% .
The separation of particles is carried
out in the depth structure of the
m edium on the surface of the
individual bres.
These im purities m ay include dust,
m etal abrasion or soot particles
resulting from an incom plete com -
bustion process. In addition to the
solid particles, the lters also have
to rem ove w ater residues in the
fuel pipes as w ell as oil drops
w hich result from the blow -by-gas
of the crankcase air vent ventilation/
recirculation system .
2.1 Filtration effects
A variety of different m ethods are
used to separate dirt particles.
These effects w ill be explained in
the follow ing chapters: They m ainly
depend on the size of the particle
to be separated as w ell as on the
properties of the liquid or gas con-
taining them . Physical effects, such
as centrifugal or electrostatic forces,
also play a m ajor role in the separa-
tion process.
In the follow ing gures, the lter
m edium is represented as an indivi-
dual bre perpendicular to the plane
of the gure. A ir, oil and fuel m ove in
a lam inar ow around the bre and
are show n by sim ple path curves
(stream lines).
The barrier effect is the m ost im por-
tant separation m echanism in the l-
tration of oil and fuel. In air ltration,
the inertia and diffusion effects also
play roles in addition to the barrier
effect.
Inertia effect
2.2 Inertia effect
The inertia effect is based on the
fact that dirt particles w ith a larger
m ass approaching the bre leave
their stream line path as a result of
inertia and directly collide w ith the
ﬁ bre.
individual ﬁber:
axis perpendicular to
the plane of the ﬁgure
stream lines
direction of ﬂow
dirt particle
stream lines
8
B A SIC S O F FILTR ATIO N
individual ﬁber:
axis perpendicular to the plane
of the ﬁgure
stream lines
direction of ﬂow
stream lines
individual ﬁber:
axis perpendicular to the plane
of the ﬁgure
stream lines
direction of ﬂow
smaller particle
which can follow
the stream lines
stream lines
2.3 Barrier effect
In the barrier effect, the particles
can follow the stream line path due
to their size. B ut if they get too
close to and com e into contact w ith
the bre, they adhere to it (Van-der-
W aals forces).
2.4 Diffusion effect
The diffusion effect is used to ltrate
very sm all dirt particles w ith a dia-
m eter of less than 0.5 µm : They
m ove on irregular paths (B row nian
m ovem ent), collide w ith a bre m ore
or less accidentally and adhere to it.
Barrier effect
Diffusion effect
9
1 2 3 4 5 7 6
D IRT LO A D A N D PR ESSU R E D IFFER EN C E
3
W hen using a new lter, dirt
particles rst settle on the bre
surface. W ith increasing contam ina-
tion, the thickness of this dirt layer
increases and causes a decrease
in the pore volum e. B ut w ith the pore
volum e decreasing and the ow
rem aining constant, the pressure
difference rises.
The developm ent of the pressure dif-
ference ∆p is illustrated in the follo-
w ing diagram as a function of the
operating tim e and the dirt load:
The rather slow increase in the pres-
sure difference is a typical pheno-
m enon w ith depth lters. O nly w hen
the pore volum e of the lter is nearly
exhausted does the pressure diffe-
rence rapidly increase. This is w hen
the lter should be replaced. The
tim e t
1
is speci ed in the data sheets
by the car m anufacturer.
Filters usually have to collect m icro-
scopic particles. The follow ing gure
illustrates the different sizes of typi-
cal dirt particles w hich a lter has to
deal w ith:
In order to illustrate the dim ensions
of ltered particles even better, dirt
particles and pollens are show n in
com parison w ith the cross-section of
a hum an hair.
Development of the pressure difference
Dimensions of various particles
Proportions
fog
smoke road dust
pollen
exhaust gases
bacteria
soot
spores
1 human hair (~70 µm)
2 minimum
human vision (~40 µm)
3 white blood corpuscle (~25 µm)
4 pollen (~10 µm)
5 dirt particle
6 red blood corpuscle (~7 µm)
7 bacterium (~2 µm)
latest time for
ﬁlter replace-
ment
max. pressure difference ∆p
t
1
operating time/dirt load
p
r
e
s
s
u
r
e

d
i
f
f
e
r
e
n
c
e

∆
p
10
TH E FILTER M ED IU M
4
Since paper is the num ber one
ﬁ lter m edium in m otor vehicle
technology, it w ill be exam ined m ore
closely in the follow ing chapter.
This brochure does not include
a detailed description of ltration
m ethods using ne-m eshed sieves,
felt or eece fabrics.
The types of tim bers m ost often used
to produce lter paper are oak,
m aple and alder am ong the hard-
w oods; spruce and ceder w oods pre-
dom inate in the range of softw oods.
D epending on the application, high
quality lter paper differs in the
4.1 Requirements on
the ﬁlter paper
The requirem ents on the lter
m edium are
■ a high pulsation stability at any
dynam ic load
■ insensitiveness to w ater (e. g. in
case of heavy rain or spray),
engine oils, crankcase gases and
fuel vapors, as w ell as
■ a high therm al stability, since the
ﬁ lter elem ent m ay be exposed to
tem peratures of up to 80°C during
operation.
In order to counteract these m echa-
nical, clim atic and therm al loads, the
ﬁ lter papers are im pregnated: the
paper is soaked in m odern synthetic
resins and then subjected to a heat
treatm ent. D uring this process, the
pore volum e, pore size and ber
structure of the original m aterial m ust
rem ain unchanged.
4.2 Forming
In order to accom m odate a m axim um
ﬁ lter surface in a cartridge, the paper
is form ed during heat treatm ent. In this
operating procedure, a certain pleat
shape is forced onto the paper by
m aking use of the paper‘s therm opla-
stic behavior betw een 20 und 100°C
so that the pleat shape is preserved
even during curing.
This pleat geom etry m akes it possible
to obtain an effective lter surface area
of approx. 10 m in a truck lter
cartridge, for exam ple. In order to pre-
vent the pleats from sticking to each
other in the engine environm ent, pleat
spacers are form ed into the paper.
A nother possibility consists in giving
each pleat a corrugation, thus preven-
ting the paper from bridging.
Pleat geometry
com position of the ber and pore
structure as w ell as in its neness.
The three m ost im portant lter m edia
are cotton, cellu-
lose and plastic
ﬁ bers.
11
1
2
3
4 6 7 8 9
10
5
TH E FILTER M ED IU M
4.3 Quality testing of ﬁlter papers
The lter paper is subjected to rigid
quality controls.
O ne of the m ost im portant test proce-
dures is the so-called bubble test.
Putting it sim ply, this test consists of
soaking the test paper w ith a pre-
cisely deﬁ ned liquid and subjecting
it to different test pressures. Exact
docum entation of the test conditions
is very im portant. The rst air bubble
can m athem atically be assigned to
the largest pore. W hen the test piece
is com pletely covered w ith air bub-
bles, this indicates the average dis-
tribution of pore sizes. The reason:
„Large pores require low pressure
loads, sm all pores require high pres-
sure loads.“
This m ethod is also used to deter-
m ine the pressure difference. The test
is relatively sim ple to execute, but its
results are still very exact. It has to
be kept in m ind, how ever, that the
test only provides com parative values
w ith other papers. In addition, sepa-
ration tests w ith test particles are car-
ried out (direct m ethod according to
D IN ISO 5011).
The follow ing gure show s the test
set-up for the determ ination of the
degree of separation and the dust
capacity of lter elem ents.
air ﬂow
air ﬂow
1 dust injector
2 inlet pipe
3 casing for dust addition
4 outlet pipe
5 pressure meter
6 absolute ﬁlter
7 volume ﬂow meter
8 volume ﬂow control device
9 suction blower
10 ﬁlter
Test set-up to determine the separation degree
12
A IR FILTER S
5
W hen talking about air lters
(inlet lters) in today‘s engine
technology, the m ain focus lies
on the so-called dry lters, the
generic term for a variety of
exchangable paper lters.
D ry lters are based on the opposite
operating principle than w et or oil
bath lters, w here liquids are used
to separate dust particles from
the inlet air.
The paper lter has gained accep-
tance m ainly because it can ensure
higher and - above all - stable sepa-
ration degrees for all load ranges.
A dditional advantages are the easy
m aintenance and the independence
of the installation position. From the
environm ental standpoint, too, the
paper lter is increasingly gaining
acceptance.
5.1 Task / function
It is the general task of air lters
to purify the inlet air and to m uf e
the inlet noise of the engine. A nother
function - especially in passenger
cars - consists in pre-heating the inlet
air and controlling the tem perature.
This regulation is essential for the
operating behavior of the engine and
the com position of exhaust gases.
A short num erical exam ple w ill illus-
trate the capacity and im portance of
the lter elem ent: D epending on the
landscape, w eather conditions, soil
and road properties and the use of
the vehicle, the am ount of dust per
m ³ of air m ay range from 1 to 10 m g.
O n unpaved roads or on construction
sites, it m ay even reach 40 m g. A ssu-
m ing that a supply of approxim ately
14 kg of air is necessary for the com -
plete com bustion of one liter of fuel
(spark ignition engine), one gets an
idea of how m any dust particles have
to be ltered out. This am ount of dust,
together w ith the lubricant, can form
an abrasive m ass w hich inevitably
leads to a considerable w ear of the
pistons, piston rings and cylinder bar-
rels.
5.2 Consequential damage
A failure to replace air lters in tim e
leads to a richer fuel-air m ixture and
thus to a higher em ission of pol-
lutants as w ell as a low er engine per-
form ance.
Fine dust particles that pass the
ﬁ lter paper contribute to siltation in
the engine and m ay deposit on the
air m ass sensor. This com ponent is
installed on the clean-air side of the
inlet lter and is responsible for pro-
portioning the am ount of fuel (increa-
sing fuel consum ption).
If dirt particles get into the inside
of the com bustion cham ber, the life-
tim e of the engine is reduced since
the plain bearings, pistons, piston
rings and cylinder barrels w ear out
due to the increased abrasive effect.
5.3 Design
5.3.1 Air ﬁlters for passenger cars
A ir lters for passenger cars com e in
tw o different designs: as panel lters
and as round lters (round and oval
elem ents). The type of lter w hich is
suitable for any speci c case m ainly
depends on the application of the
basic rules of lter technology.
For their position in the vehicle, the
spot w ith the low est possible dust
or w ater supply is chosen. The lter
elem ents have a high separation
degree w hich is independent of the
load. Their replacem ent is sim ple
and is determ ined by the m ainte-
nance dates speci ed by the vehicle
m anufacturer.
There is a w ide range of engines
on the m arket, and each vehicle
requires lters w hich exactly ful ll
the requirem ents of the engine and
installation space. K S offers air lters
w ith suitable designs for virtually any
vehicle. Filter casings and lter ele-
m ents are optim ally m atched and
adjusted to the engine type and
its inlet system .
A special design for a panel lter is
show n in the picture below . In addi-
tion to the lter paper, the lter is
protected by a eece for rough l-
tration. This design is predom inantly
used in areas w ith a heavy dust load.
Panel air ﬁlter Round air ﬁlter Panel air ﬁlter with protecting ﬂeece
13
A IR FILTER S
5.3.2 Air ﬁlters for
commercial vehicles
D ue to the higher ow rate and less
critical sealing of the lter casing
periphery, cylindrical round lters
w ith a steel or plastic m esh are
predom inantly used in com m ercial
vehicles. These lters are divided
into single-stage and tw o-stage air
ﬁ lters. In contrast to single-stage l-
ters, tw o-stage lters are equipped
w ith a cyclone-type cleaner as a
pre-separator.
The cyclone cleaner takes advan-
tage of the effects of centrifugal
forces: The air stream is set into rota-
tion by a speci cally designed rotor
disk w ith so-called baf es. D ue to
the centrifugal forces, the dirt parti-
cles are precipitated tow ards the w all
of the casing. From there, they are
either routed to the outside or are
collected in a collector tank, depen-
ding on the design of the lter.
Especially in construction m achines,
som e lters are equipped w ith an
additional secondary elem ent (safety
elem ent). It is used to protect the
engine w hen the m ain elem ent is
dam aged or being serviced. The
secondary elem ent m ay not be inser-
ted w ithout the m ain lter and
should be exchanged w ith every third
replacem ent of the the m ain elem ent.
Since these lters com bine the tasks
of ltration and suppression of noise,
they are called silenced lters.
In com m ercial vehicles, the air intake
is often located above or beside the
driver‘s cabin. This helps keeping the
am ount of dust in the intake air as
low as possible and thus extends
the m aintenance intervals. In m odern
trucks, the lter casings are fre-
quently designed larger than neces-
sary for ltration. This m easure helps
reduce the intake noise considerably.
This pre-separator helps to prolong
the service life. B oth lter types
are usually integrated in one casing.
The tw o-stage lter is m ainly used
in construction and agricultural
m a chines.

max. pressure difference ∆p
time
∆
p

(
b
a
r
)
single-stage ﬁlter
two-stage ﬁlter
Air ﬁlter for commercial vehicles
Different service lives
14
1
2
3
5.4 Mounting instructions for ﬁlter
replacement
Please keep in m ind the follow ing
advice w hen replacing an air lter:
■ N ever exchange the air lter w ith
the engine running.
■ M ake sure that no dirt particles
get into the air ducts w hen rem ov-
ing the old lter.
■ D o not try to clean the old lter by
using com pressed air.
■ C hoose the right lter. Serious
dam ages m ay otherw ise occur on
the engine due to different sealing
and perm eation properties.
■ Follow the instructions given by
the m anufacturer w hen installing
the new lter.
■ B evor installation, clean the cover
and casing of the new lter using
a clean and soft cloth. D o not use
a brush or other instrum ents that
m ight w hirl up dirt particles.
■ Exam ine all gaskets for dam ages.
Even sm all cracks or deform a-
tions can lead to considerable
contam ination. If in doubt, replace
the gaskets.
■ Place the lter elem ent in the
center of the system .
■ W hen m ounting the cover, m ake
sure that there is no gap betw een
the cover and the casing because
unﬁ ltered air m ay otherw ise enter
the com bustion cham bers.
Important note:
In case of frequent rides on very
dusty roads, the air lter cartridge
m ust be exchanged m ore often than
prescribed under norm al circum -
stances.
A tw o-stage air lter for a com -
m ercial vehicle is show n in the
follow ing gure. It consists of a
deﬂ ector (baf e) (1), the m ain lter
elem ent (2) and a safety elem ent
(3). The intake air enters the lter
through the outer shell, and the
puri ed air leaves it through the
interior.
A IR FILTER S
Two-stage air ﬁlter
15
A IR FILTER S
5.5 Handling mistakes
The lter m ay not be cleaned
by using com pressed air under
any circum stances. This w ould
press the m icroscopic dirt par-
ticles even further into the
depth structure of the lter
paper, resulting in an even
low er ow rate. In addition, the
ﬁ lter paper m ay tear due to the
high air pressure.
W hen handling the lter, also
pay attention that
a) the paper pack and
b) the sealing area are not
destroyed.
In case of insuf cient sealing
or cracks in the lter paper,
foreign m atter w ill enter the
inside of the engine and m ay
cause serious dam ages.
Filters w ith the defects m en tioned
above m ay not be installed under
any circum stan ces.
16
A IR D RYER
6
The air dryer serves for a
special type of ltration. It is
m ainly em ployed in com pressed-air
system s for m edium -size and heavy
com m ercial vehicles. Since com -
pressed air is used as an energy
carrier for m any control processes,
it m ust be ensured that the hum idity
of the air does not cause corrosion
in the pipes and tanks or even para-
lyzes the w hole system at freezing
tem peratures. The air dryer is there-
fore one of the safety-relevant com -
ponents in the vehicle.
Mounting position
of the air dryer
6.2 Consequential damage
If w ater and oil enter the tanks
and thus the braking system , the
consequences w ill be dangerous
and costly dam ages: The m oisture
dam ages the valves, causes corro-
sion in the pipes and tanks, and at
sub-zero tem peratures the com plete
system m ay freeze. The oil affects
the function of the valves and delays
the response of the brakes. The
brake linings are therefore used in
excess and w ear faster.
In order to prevent these potential
dam ages and costs, the use of a
K S air dryer is highly recom m ended.
The life tim e of the individual com po-
nents rises, and the vehicles have
few er dow ntim es.
Therefore, the air dryer should be
exchanged regularly as well!
Granulate developed
especially to remove
humidity from the air
6.1 Function
The com pressed air necessary for
braking is produced by the com pres-
sor w hich is pow ered by the engine.
It then ow s from the com pressor to
the one-cham ber air dryer provided
w ith a pressure control device. The
com pressed air is dryed using a spe-
ci cally developed granulate, and the
pressure in the braking system is lim i-
ted to a speci ed value by an inte-
grated pressure control system .
Then the com pressed air ow s into
a com pressed-air tank w hich is
equipped w ith a condensed w ater
sensor to m onitor the drying process,
as w ell as a safety valve.
17
FU EL FILTER S
7
Fuel lters are a crucial part in
today‘s highly sophisticated fuel
supply system s. Since they com e
in various designs, the different fuel
7.1 Structure of different fuel
systems
7.1.1 Spark-ignition engines
In m odern spark-ignition engines, w e
distinguish betw een direct and indi-
rect injection.
Indirect injection (Induction pipe):
Electrom agnetic injection valves are
used to inject the fuel into the induc-
tion pipe or directly into the cylinder.
Injection pressures of 3-4 bar are
currently used, and the fuel pressure
is kept constant by a pressure con-
trol valve. The nom inal ow rate
7.1.2 Diesel engines
The com bustion process in a D iesel
engine differs considerably from that
of a spark-ignition engine. The diesel
engine alw ays operates w ith internal
m ixture form ation and self-ignition of
the fuel-air m ixture. The term „internal
m ixture form ation“refers to the pro-
cess of converting liquid fuel into
an ignitable m ixture after injection.
In order to obtain a better and m ore
ef cient com bustion process, the fuel
is directly injected into the cylinder
in virtually all m odern D iesel engines.
Pum p-nozzle as w ell as com m on-rail
technology are the state-of-the art
injection system s today.
system s w ill be explained at rst.
Pump-nozzle system:
In the pum p-nozzle
system , each engine cylin-
der has a pum p-nozzle
elem ent. It contains the
follow ing com ponents in
its casing :
■ the high-pressure piston
pum p elem ent,
■ the solenoid valve to
control the injection pro-
cess, as w ell as
■ the injection nozzle w ith
the injection valve.
This system is suitable for
injection pressures of up to
2000 bar.
Recommended minimum ﬁlter ﬁneness in spark-ignition and Diesel engines
Common Rail:
The com m on-rail technology uses a
high-pressure injection system w ith
electric control and a com m on fuel
rail. The fuel is fed to the com bustion
cham bers by injectors w hich are
controlled by solenoid valves. W ith
a high-pressure radial-piston pum p,
pressures of up to 1600 bar can be
reached.
D ue to the use of these m odern
system s, it has becom e necessary
to increase the neness of fuel lters
considerably.
A high-pressure pum p is used to
take the fuel, w hich has a pressure
of up to 120 bar, to a pressure reser-
voir w hich is directly connected to
the injection valves.
B ecause of the high pressures and
the large num ber of additional com -
ponents such as the pressure reser-
voir, sensor or control valves, these
ﬁ lters are m uch ner than the lters
used in indirect injection.
Simple Diesel injection
100
75
50
25
0
carburetor indirect injection direct injection pump/nozzle common rail
d
e
g
r
e
e

o
f

s
e
p
a
r
a
t
i
o
n

(
3
-
5

µ
m
)

i
n

%
of the fuel lter is designed m uch
higher than necessary for the actual
fuel consum ption.
Direct injection:
For direct injection, substantially
higher injection pressures are neces-
sary. The supply system in these
system s consists of a low - and a
high-pressure circuit. The low -pres-
sure circuit has an integrated electric
fuel pum p and is only used to feed
the high-pressure circuit. The preli-
m inary pressure usually has a value
of approx. 3.5 bar.
injection
nozzle
return
pipe
sieve
ﬁlter
injection
pump
leakage oil
pipe
overﬂow
valve
fuel ﬁlter
1 ... 1,5 bar
350 ... 1000 bar
overﬂow
valve
fuel pump
fuel tank
18
FU EL FILTER S
7.2 Task / function
The fuel lter has the function to pro-
tect the fuel system from im purities
such as dirt, rust, dust and w ater
contam inants in order to guarantee
a proper engine perform ance. The
protection of high-quality injection
system s is especially im portant in
m odern D iesel engines. Even parti-
cles w ith dim ensions in the range
of 5-20 m icrons m ay lead to serious
dam ages, including engine break-
dow n.
The fuel lter has a ner lter paper
than the oil lter since the com pon-
ents of the fuel supply system have
sm aller clearances. In order to pre-
vent even m inute dirt particles from
entering the pipe circuit, by-pass
valves are not allow ed in fuel lters.
Spin-on fuel ﬁlter Fuel ﬁlter cartridge Fuel pipe ﬁlter (inline)
7.4 Consequential damage
Fuel lters have to be exchanged
regularly. If the lter is clogged, the
fuel supply of the engine is insuf cient
and leads to a loss of pow er. D if -
culties in starting occur, the engine
stutters and runs irregularly; there is
not enough fuel for acceleration.
If a lter is used w hich is not suitable
for the corresponding application or if
the lter installed has quality deﬁ cien-
cies or im perfections, a higher am ount
of dust enters the lter elem ent. In
spark-ignition engines, this leads to
faults in the carburetor or injection
system and causes w ear on these
com ponents. In D iesel engines, the
extrem ely sensitive injection elem ents
are dam aged and fail.
7.3 Arrangement of the ﬁlters
A ccording to their arrangem ent, fuel
ﬁ lters are divided into one-stage,
tw o-stage and parallel lters.
In a tw o-stage lter, a coarse lter
(sieve lter of m etal or plastic) is
m ounted in front of the ne lter.
The parallel lter consists of tw o
identical lter cartridges. It has the
advantage of allow ing a higher ow
rate than the one-stage lter.
Two-stage ﬁlter Parallel ﬁlter
coarse ﬁlter ﬁne ﬁlter
fuel ﬂow
2 identical ﬁlter cartridges
fuel ﬂow is divided
7.5 Design
The range of K S fuel lters includes
spin-on lters, lter cartridges, and
fuel pipe lters.
19
FU EL FILTER S
W ith respect to the arrangem ent in the
casing, the paper cartridges are divi-
ded into spiral lters (axial lters) and
star lters (radial lters).
In axial lters, the paper is w ound
around a pipe. The paper strips are
arranged in such a w ay that they form
open V-shaped bags in w hich the dirt
particles are collected. The inlet fuel
axially ow s through the lter from top
to bottom , and the puri ed fuel is drai-
ned upw ards through the central pipe.
In radial lters, the paper is arranged in
a star form around a pipe of perforated
m etal. The fuel radially ow s through
the lter to the inside, and dirt particles
are retained on the paper surface.
The ltered fuel is drained through the
open ings of the inside pipe.
Axial ﬁlter Radial ﬁlter
7.5.1 Fuel ﬁlter cartridge
They can be exchanged individually
and are installed in an extra casing
w hich is m ounted on the engine.
W hen replacing the lter, the cover
of the casing is unscrew ed, and
only the lter elem ent is exchanged.
M odern lter cartridges are m ade of
m aterials that are suitable for therm al
recycling (see chapter 9, m etal-free
ﬁ lter cartridges)
C artridges from paper and felt are
used as lter elem ents.
Filter cartridge from paper Filter cartridge from felt
7.5.2 Fuel pipe ﬁlters (inline)
Fuel pipe lters are designed as
sieve or paper lters and are
installed in the fuel pipe. D epending
on the application, the lter casing
is m ade of alum inium , sheet steel, or
plastic.
Sieve lters are e. g. used as preﬁ l-
ters in the fuel tank or in the fuel
pum p. They consist of a ne w ire or
polyam ide m esh w hose w idth varies
from 40 to 60 µm .
For ne ltration, paper lters
be tw een 6 and 10 µm are used.
They are usually m ounted by just
slipping them onto the fuel pipe.
ﬁltered outlet fuel
central pipe
unﬁltered
inlet fuel
outlet
fuel
inside
pipe
inlet
fuel
ﬁlter paper
ﬂow towards the inside pipe
20
FU EL FILTER S
7.6 Mounting instructions for ﬁlter
replacement
A lw ays take the utm ost care w hen
w orking on the fuel system . The fuel
system often rem ains under pressure
for a long tim e after the engine w as
stopped!
■ O bserve the exchange intervals
recom m ended by the m anufac-
turer.
■ A lw ays observe the m ounting
instructions given by the vehicle
m anufacturer.
■ U se suitable tools for lter replace-
m ent.
■ Pay close attention to the ow
direction w hen installing fuel-pipe
ﬁ lters. The ow direction is
m arked w ith an arrow and should
point aw ay from the tank tow ards
the engine.
Important note
W hen replacing the fuel pum p,
alw ays exchange the lter also.
R eplacing the relatively cheap lter
helps prevent large and expensive
repairs!
7.5.3 Spin-on fuel ﬁlters
Spin-on fuel lters consist of a
casing w ith a lter elem ent, w hich
are exchanged as a unit during
m aintenance. The lters are norm ally
m ounted in the engine com partm ent
Water separation:
D ue to its high surface tension, the
w ater is rst retained on the soiled
side. A fter a rise in the pressure dif-
ference, it passes through the pores
to the clean side, w here it form s
larger drops. B ecause of their higher
speci c gravity, the drops fall into
the w ater collection cham ber. B y
opening the w ater drain plug, the
w ater can be drained. In som e
vehicles, a sensor gives inform ation
on the w ater level.
Structure of a Diesel spin-on ﬁlter
or under the vehicle betw een the fuel
tank and the engine.
In passenger cars, lters w ith a
w ater drain plug and an integrated
pressure control valve are used in
addition to the standard, replaceable
cartridge lters. For com m ercial
vehicles, special designs are offered
w ith integrated extra functions such
as:
■ valves or sensors to control the
pressure and tem perature,
■ electric heaters,
■ heat exchangers, or
■ w ater sensors w ith a w ater collec-
tion cham ber.
gasket
fuel intake
filter cover from
galvanized sheet steel
fuel outlet
ﬁlter medium
supporting pipe
pressure-proof ﬁlter casing
water collecting chamber
water drain plug
drain pipe
21
O IL FILTER S
8.1 Task / function
W hile the air lter has the function to
keep w ear-enhancing dirt particles
from entering the engine, the oil lter
is used to lter out the particles that
have already entered the engine.
These im purities m ay include w ear
m etals, dust particles from the
com bustion air, soot and corroded
m etals.
O il lters do not have an inﬂ uence on
chem ical or physical changes in the
oil during engine operation because
they are not capable of rem oving
liquid or dissolved particles.
B ut they help to prevent an early
w ear of the engine‘s sliding sur-
faces. W ithin the m aintenance inter-
vals, they preserve the function-
ability of the engine oil since
they have a positive inﬂ uence
on its viscosity and pum pability.
Since hydraulic system s are playing
an everm ore im portant role in
m odern vehicles, oil lters have
en tered this area, too. Especially in
hydraulic steering system , they are
increasingly used.
8.2 Arrangement
A ccording to their arrangem ent in
the oil circuit, w e distinguish
be tw een full- ow and partial- ow oil
ﬁ lters as w ell as a com bination of
both.
8
Filter system s in the engine cir-
cuit are very im portant com po-
nents in m odern vehicles. They con-
siderably contribute to reaching the
desired engine life.
The m ain oil gallery is
responsible for the oil
supply of the plain bea-
rings, w hereas the con-
necting-rod bearings and
pistons are supplied w ith
oil by the crankshaft. In
addition, oil is also fed to
the cylinder head in order
to lubricate the cam shaft
and the operating ele-
m ents of the valves. In a
charged engine, part of
the oil is used to lubricate
the turbocharger. Full- ow
oil lters are preferably
used because all of the
oil has to pass through
the lter elem ent. It is
thus ensured that im pu-
rities can already be l-
tered out during the rst l-
tration process.
This arrangem ent has the
disadvantage, how ever,
that the lter has to acco-
m odate the w hole oil ow .
Full- ow oil lters m ust
have a by-pass valve and
should alw ays be m ounted
behind the pressure con-
trol valve.
The partial- ow lter is
installed in a pipe
arranged in parallel to
the full ow pipe.
This pipe is m ounted
be tw een the lubricating
points and the feed pum p.
D ue to an upstream
throttle, only a part of
the oil supply (5 -10% )
passes through this lter.
Therefore, only partially
puri ed oil reaches the
lubricating points.
B ecause of its low feed
and ow rate, the partial-
ﬂ ow lter does not reach
the highest possible rate
of ltration. It should there-
fore be regarded as a ne
ﬁ lter w ith a high degree of
separation.
8.2.1 Full-ﬂow oil ﬁlters
8.2.2 Partial-ﬂow oil ﬁlters
overﬂow valve
pressure gauge
oil sump
full-ﬂow oil ﬁlter
relief pressure valve
oil pump
point of
lubrication
pressure
gauge
oil sump
relief pressure valve
oil pump
point of
lubrication
throttle
Full-ﬂow oil ﬁlters
Partial-ﬂow oil ﬁlters
22
8.2.3 Oil ﬁlters in a combination
system
If partial- ow lters are used in com -
bination w ith full- ow lters, a very
effective ltration is achieved: M inute
particles that have passed the full-
ﬂ ow lter are rem oved by the partial-
ﬂ ow lter. The partial- ow lter offers
a very intense puri cation w ith a high
degree of separation. A s a
partial- ow lter, the free-jet cen-
trifuge (oil splash lter) is m ainly
used in com m ercial vehicles and
building m achinery.
The oil w hich is diverted from the
full- ow channel to the partial- ow
channel ow s through the hollow
rotor shaft into the inside of the
ﬁ lter through several bores. It leaves
the centrifuge through speci cally
designed discharge nozzles.
In this process, reaction forces are
released w hich set the rotor into
rotation. D epending on the pressure
and tem perature, the rotor can reach
a speed betw een 4000 and 8000
1/m in. D ue to the centrifugal forces
O IL FILTER S
em erging during rotation, the
dirt particles in the oil are
throw n tow ards the inside
w all of the rotor, w here they
rem ain stuck until the cen-
trifuge is exchanged during
m aintenance.
8.3 Consequential damage
A brasive dirt particles that have
entered the inside of the engine due
to insuf cient ltration m ay cause
scores on pistons and piston rings
as w ell as bulgy cylinder w ear. This
m ainly affects the sharp edges of the
piston rings (see chapter 4, W ear on
engine com ponents).
D ue to an insuf cient sealing of the
com bustion cham ber, the pressure
8.4 Design
O il lters are available w ith tw o differ-
ent designs - as spin-on lters and
casing lters.
Spin-on oil ﬁlter Oil ﬁlter cartridge/ hydraulic oil ﬁlter
in the crankcase is increased by
com bustion gases that pass the
piston.
This excess pressure causes a
loss of oil at the sealing spots
and oil leakages at the intake-valve
guides. A nother consequence is
the reduction of com pression and
engine pow er. The connecting-rod
and crankshaft bearings can also
be substantially affected by the abra-
sive effects of the dirt particles.
A higher clearance of the bearings
caused by abrasion reduces their
supporting capacity and m ay lead to
bearing dam age.
oil cooler
oil pump
relief pressure
valve
throttle
partial-
ﬂow oil
ﬁlter
oil sump
point of
lubrication
overﬂow valve
full-ﬂow oil
ﬁlter
oil outlet bores
hollow shaft
4000 - 8000
1 /min
rotary disk
with special
arrangement of
outlet nozzles
oil ﬂow
partial-ﬂow
duct
CF*
bearing
rotor
dirt
layer
CF*
Free jet centrifuge CF = centrifugal force
Oil ﬁlters in a combination system
full-ﬂow oil
ﬁlter
23
O IL FILTER S
8.4.1 Spin-on oil ﬁlters
The spin-on oil lter consists of a
ﬁ lter casing (from sheet steel), a lter
elem ent and a cover w hich is
usually anged or w elded to the
ﬁ lter. The w hole lter elem ent is
exchanged w hen replacing the lter.
M any replaceable cartridge lters
are additionally equipped w ith a so-
called by-pass valve (over ow valve)
as w ell as a anti-drain valve. This
type of lter is used in passenger
cars as w ell as in com m ercial
vehicles.
By-pass valve
The by-pass valve, also called over-
ﬂ ow valve, has the function to open
a direct passage to the oil circuit
in case of an elevated oil pressure.
A lthough unﬁ ltered oil is fed to the
circuit, this is still better than a com -
plete interruption of the lubricating oil
supply. The by-pass valve can be
installed in front of the full- ow valve
or - as in m any K S lters - directly
into the lter elem ent. The set value
of the opening pressure is approx.
1-2 bar in practice, depending on
the application.
The set value can be exceeded
during the cold-running phase of the
engine (highly viscous oil) or if the
ﬁ lter is very dirty and has reached
the end of its service life.
Anti-drain valve
The anti-drain valve is another cons-
tructive feature of replaceable-cart-
ridge lters. D epending on the instal-
lation position of the oil lter, it m ay
8.4.2 Casing ﬁlters
In contrast to the spin-on lter, the
casing of these lters is screw ed
onto the engine or constitutes an
integrated part of the crankcase.
O nly the cartridge is exchanged in
this type of lter. In m odern vehicles,
these lters are m ade of m etal-free
m aterials. D ue to their environm en-
tally friendly disposal, these lters
are gaining m ore and m ore im por-
tance (see chapter 9, M etal-free lter
cartridges).
be integrated into the intake or drain
pipe. It prevents the oil lter from
running dry during a standstill of the
engine.
by-pass valve
open closed
engine
standstill:
anti-drain
valve closed
operating
engine:
anti-drain
valve open
anti-drain
valve
Structure of a spin-on oil ﬁlter
Function of a by-pass valve and anti-drain valve
ﬁlter element
ﬁlter casing
by-pass valve with protecting sieve
supporting pipe
anti-drain valve
ﬁlter cover
24
O IL FILTER S
8.5 Failure of the oil ﬁlter due to
excess pressure
If a lter is bent or sw ollen, a lack of
ﬁ lter quality is often assum ed. H ow -
ever, this is only very rarely the case.
A deform ed lter m ostly is a sym p-
tom for problem s in the oil circuit.
The fault is often caused by the pres-
sure control valve, w hich is usually
integrated in the oil pum p. The oil
pum p provides the required oil pres-
sure for the lubrication system in
order to build up a lubricating lm
betw een the high-duty engine parts.
The pressure control valve has the
function to m aintain the pressure in
the lubricating system at a certain
value.
A fter the valve is opened, the
pressure in the lubricating system s
rem ains alm ost constant.
If the pressure control valve is
jam m ed or reacts slow ly w hen the
engine is started, an inadm issible
excess pressure is caused in the
system .
If the valve does not open at all,
the pressure continues to increase
and deform s the w eakest part in the
system - the lter: The gasket is
cracked and the fold breaks if the
ﬁ lter is m ounted very tightly.
Since this usually also causes a
leakage of engine oil, the engine
m ust im m ediately be stopped to
prevent m ore serious dam age.
8.6 Mounting instructions for
ﬁlter replacement
N o oil change w ithout lter
exchange: W henever exchanging
the oil, also exchange the oil lter.
■ D rain the engine oil w ith the
engine at operating tem perature
so that the oil sum p is em ptied
com pletely and the largest pos-
sible am ount of foreign m atter is
w ashed out.
■ U se special spanners for dis-
m ounting.
■ C om pletely rem ove all gaskets
residues from the engine‘s m ount-
ing face and carefully clean the
m ounting faces.
■ Thoroughly clean the lter
casings of lter cartridges.
■ A lw ays use new gaskets w hich
are included in the scope of
delivery. If the old gasket is re-
used, proper sealing cannot be
en sured.
■ Spread engine oil onto the gas-
kets. N ever use lubricating grease
for this. Its com ponents m ight
attack the O -rings of the lter.
■ D o not tw ist the lter w hen putting
it onto the thread.
■ Exam ine all gaskets for correct t
before tightening.
■ O nly screw the lters m anually, do
not use tools.
■ C heck the oil level.
■ Start the engine and check the
circuit for leakages in idling posi-
tion.
Operating principle of a lubricating system
standard oil ﬁlter bent oil ﬁlter
by-pass valve
(normally
closed)
points of
lubrication
spin-on oil ﬁlter
pump
oil control
valve open
oil return
normal pressure
Deformed oil ﬁlter
25
M ETA L-FR EE FILTER C A RTR ID G ES
9
W ith the lter concept of the
EN ER G ETIC
®
series, Ing. W alter
H engst G m bH & C o. KG has devel-
oped a system that offers advan-
tages for all types of installations.
The system follow s a m odular prin-
ciple and covers a w ide variety of
applications. The advantages of the
EN ER G ETIC
®
series at one glance:
■ O nly the lter cartridge is
exchanged during service. The
ﬁ lter casing and valves rem ain on
the engine block for their w hole
service life.
■ C lean replacem ent of the lter
cartridge, the skin does not com e
into contact w ith w aste oil.
■ D esigned for extended m ainte-
nance intervals.
■ Protection of resources by using
recycled m aterials. The lter cart-
ridge only consists of the lter
m edium and therm oplastic end
disks.
■ Energetic utilization of the lter
elem ent. The energy stored in the
ﬁ lter elem ents is recovered during
com bustion.
■ Substantial reduction of service
and disposal costs. The m etal-
and glue-free lter elem ents do
not have to be subjected to an
expensive disassem bly process.
The com plete lter elem ent is suit-
able for therm al recycling.
Mounting examples for
ENERGETIC
®
ﬁlters
ENERGETIC
®
is a registered trade mark of Ing. Walter Hengst GmbH & Co. KG / Münster, Germany
AU D I V6 TD I
photo: Hengst Filterwerke
B M W M 73-V12
photo: Hengst Filterwerke
O PEL X18XE-1
photo: Hengst Filterwerke
In the m eantim e, a variety of m etal-
free lters w ith the sam e advantages
have been developed by K S.
Metal-free ﬁlter cartridge
26
C O N C LU D IN G R EM A R K S
10
K S lters are produced
using continuously m oni-
tored state-of-the-art m anufacturing
processes. O nly by these stringent
m easures can it be ensured that
they m eet the high requirem ents
of m odern precision engines. Espe-
cially in the eld of lters, the quality
is not perceptible at rst glance. It is
not easy to see if a lter w ill m eet the
desired perform ance requirem ents.
A ll K S lters at least ful ll O E require-
m ents. This ensures optim um engine
protection and a long service life.
The paper for K S lters is im pregna-
ted and subjected to pressure-proof
glueing or clasping. The pleat geo-
m etry, speci cally designed for each
application, ensures regular spacing
betw een the pleats and an optim um
utilization of the lter surface. In con-
stant controls during the m anufac-
turing process, K S lters have to
dem onstrate their quality at any tim e.
They are reliable and ef cient. Pre-
cise processing m ethods ensure an
exact t: M ounting is easy because
the gaskets and O -rings needed for
installation are included in the scope
of delivery. W ith K S lters you avoid
A ll lters and the air dryer,
together w ith all identi cation
num bers, dim ensions and
applications, can be found in
the lter catalogue and on
the M SI C D R O M .
The current lter catalogue
as w ell as the M SI C D R O M
can be ob tained
from the local K S
distributors.
early abrasive engine w ear, prevent
high fuel consum ption and poor
engine perform ance as w ell as poor
em ission gures.
So, remember to exchange ﬁlters
regularly.
For European vehicle applications, a
w ide range of reliable rst-class K S
ﬁ lters is available.
Therefore: KS oil ﬁlters, KS air ﬁl-
ters and KS fuel ﬁlters
For your
information
27
G LO SSA RY
Absolute ﬁlter
com ponent in the testing procedure according to D IN ISO 5011: dow nstream
ﬁ lter w hich is installed to separate the am ount of dust that has passed
through the test piece
Additive
chem ical substance added to liquids to obtain certain properties or to
im prove perform ance characteristics
bar
m easurem ent unit of pressure: 1 bar = 10 kPa
Burst pressure
pressure difference at w hich a lter or lter com ponent is destroyed due to
the inside pressure load.
Blow-by gas
leakage ow that enters the crankcase due to insuf cient sealing betw een
the pistons, piston rings, and cylinder w all.
Brownian molecular movement
irregular zigzag m otion of m icroscopic particles (e. g. dust particles) w hen
suspended in gases or liquids, discovered by English botanist R obert
B row n; the m otion is caused by irregular collisions w ith the m olecules of the
surrounding m edium .
By-pass valve
also called over ow valve. U sually installed in the lter, the by-pass valve
offers protection in case of excess pressure
Centrifugal force
the force that acts outw ards on any body as it rotates and is directed aw ay
from the axis of rotation
Degree of separation
percentage of particles a lter can separate. A distinction is m ade betw een:
■ total degree of separation: refers to all dirt particles w ithout distinction
betw een different grain sizes
■ fractional degree of separation: this m easurem ent unit requires the indica-
tion of the distribution of grain sizes
Dirt-holding capacity
am ount of dirt a lter m edium can hold before reaching a speci ed pressure
difference
28
G LO SSA RY
Filter ﬁneness
diam eter of particles w hich are just sm all enough to pass through the pores
of the lter m edium
Filter service life
service tim e of a lter or other com ponent until m aintenance or replacem ent
µm (micron)
m etrical m easurem ent unit: 1 µm = 0.001 m m
Pressure difference ∆p
pressure difference betw een the lter inlet and outlet
Anti-drain valve
valve that prevents the oil from ow ing back through the inlet hole after the
engine has stopped
Van-der-Waals forces
forces of attraction betw een neutral m olecules, especially in case of close
approxim ation
Viscosity
glutinous nature of liquids resulting from an internal friction betw een m ole-
cules, tem perature-dependent
Filter Booklet
Technical
MSI Motor Service
International GmbH
Untere Neckarstraße
D-74172 Neckarsulm
Phone +49 71 32-33 33 33
Fax +49 71 32-33 28 64
Alfred-Pierburg-Straße 1
D-41460 Neuss
Phone +49 21 31-5 20-0
Fax +49 21 31-5 20-6 63[email protected] msi-motor-service.com
www.msi-motor-service.com
4 028977 397691
50 003 596-02 09/02